Air-sea coupling mechanisms in the North Pacific using high-resolution climate simulations

The air-sea coupling is the strongest in the vicinity of strong oceanic fronts, such as the Kuroshio Extension (KE) front. Recently, satellite observations have revealed the air–sea coupling in the North Pacific at ocean mesoscales between sea surface temperature (SST) and surface wind anomalies. Recent studies have also suggested that the mesoscale ocean-atmosphere coupling could influence the large scale, low frequency oceanic variability (20-40 years). Yet, the mesoscale/regional climate models fail to accurately represent the small scale ocean-atmosphere interactions. The objective of this study is to analyze the ocean-to-atmosphere feedback mechanisms using the high-resolution Weather Research and Forecasting model (WRF) in a stand-alone mode with three different sets of SST estimates with different horizontal resolution, used as a lower boundary condition, and coupling WRF with the Parallel Ocean Program (POP) eddy-resolving model through the use of the NCAR Coupler 7 software. In particular, we focus on cold-air outbreaks that intensify air-sea fluxes, surface winds, surface stability, and turbulence in the marine boundary layer. The preliminary results for the winter 1999-2000 suggest that the regional climate WRF simulations are able to predict the climate signatures as observed in the satellite data and global reanalysis data products. The study also shows that the effects of air-sea coupling are more pronounced on the surface heat and moisture fluxes than on the winds, and weaker intensity of the observed cold air outbreak events in the Japan Sea. The results also include a detailed assessment of the strength and frequency of the simulated cold air outbreaks through the use of ocean surface forcing to the atmosphere and the energy propagation from the surface to mid-to-upper levels of the atmosphere, and an index to characterize cold air outbreaks in regional climate simulations.